Most domestic petroleum reservoirs presently being discovered are not as prolific as earlier discoveries. Initially the reservoir energy may be sufficient to allow crude oil, gas and water to flow naturally to the surface. However, once the reservoir energy is depleted by production or, as in many cases, the original reservoir energy is not sufficient for natural flow, the oil well becomes non-productive by natural means. In order to recover additional crude oil reserves, artificial means of producing the well are used.
The most widely used method of artificial lift is the rod pump method. Artificial lift means are subject to failures which may be classified as either mechanical or corrosional. Regardless of the type of failure, the well has to be repaired to minimize down time and consequently lost oil production. Corrosion is probably the major cause of artificial lift failure. If corrosion can be at least minimally controlled, the savings realized by oil producers is considerable.
In the past, attempts have been made to combat corrosion by chemically treating the sub-surface equipment as it stands in the well bore. Two methods of treatment are continuous treatment and circulation treatment. In the first method a chemical injection pump is used to continually inject corrosion chemical into the tubing-casing annulus. The corrosion chemical is designed to adhere to the equipment surface, thus providing a protective barrier against corrosion. Basically, this type of treatment introduces corrosion chemical to every barrel of fluid that is produced. In the second method, the chemical is also introduced down the tubing-casing annulus. Once a specified amount of chemical is pumped, the well fluids are diverted from the flow line to the tubing-casing annulus by an arrangement of valves and piping. The well is pumped in this manner for several hours until the protective film is established on the sub-surface equipment. At this point, the well is placed back on production by diverting the well fluids back through the flow line.
Probably the most effective method of combating the corrosion is the continuous method because corrosion-inhibitor film is maintained on the equipment by continuous inhibitor injection. The problem with this method is that the chemical injection pumps available demand excessive maintenance and attention. In many instances, the pump will not inject the required amount or the pump will not inject at all. For these reasons, oil producers have become frustrated with the chemical pumps and therefore most oil producers treat their wells by the circulation method.
Corrosion experts believe that in severely corrosive atmospheric environments the sub-surface equipment also should be protected after removal from the well during well repair or servicing operations. Some oil producers pump high concentrations of oil and corrosion chemical down the tubing immediately before pulling the rods, or they coat the rods with oil and corrosion inhibitor while the rods are laying down. Other operators go one step further and attempt to coat the rods with corrosion chemical while the rods are being run in the well. This is accomplished by dumping a few gallons of chemical into the tubing and then running the rods into the well. The theory in this case is to run the rods through the chemical that has accumulated at the standing fluid level inside the tubing. However, it has been found that Pressure treating of sub-surface equipment with inhibitor greatly increases the effectiveness thereof.
Various forms of devices for applying chemical treating fluids to sub-surface well equipment heretofore have been provided. Examples of different forms of such previously known equipment as well as other similar structures are disclosed in U.S. Pat. Nos. 2,289,967, 3,378,088, 3,475,781, 3,901,313, 3,943,997, 3,958,049, 4,216,249 and 4,279,300.
However, most of these previously known forms of treating devices are either specifically designed for use in conjunction with down hole equip-ment being used to drill a well or are of a configuration which results in a treating apparatus having excessive overall height. In addition, some treating devices include an excess amount of removably engaged components including connections therebetween which are quickly loosened as a result of the jarring and jolting forces experienced by the above ground end of a well casing or tubing string during well servicing operations.
Accordingly, a need exists for an improved form of corrosion inhibiting chemical applying apparatus which may be mounted from the above ground end of a well casing or tubing string and utilized to pressure apply corrosion inhibiting chemicals to sub-surface equipment as that sub-surface equipment is run in the associated well. In addition, a corrosion inhibiting chemical applying apparatus including a minimum of removably joined components is needed in order to withstand the high jarring and jolting forces developed at the well head during well servicing operations.